Unit 3: Modals, Infinitives and Gerunds

I. Orientation — Non-finite Forms and Modal Meaning

Modals, infinitives, and gerunds expand the verb system beyond simple tense. Modals express meanings such as possibility, obligation, permission, and deduction, while infinitives and gerunds are non-finite verb forms that can function within larger phrases without independently marking person or tense.

• Modal principle: A modal modifies the meaning of another verb rather than naming the main action: She must leave expresses obligation or deduction.
• Non-finite principle: An infinitive or gerund does not normally agree with a subject:
  • Infinitive: to write, to have written.
  • Gerund: writing, having written.
• Basic convention: A central modal such as can, may, must, or should takes the bare infinitive: can speak, not can to speak.
• Functional distinction: Infinitives commonly indicate intention, purpose, or potential action; gerunds commonly present an activity as an experience, process, or concept.
• Time convention: Simple non-finite forms usually express simultaneous or later action, whereas perfect forms mark an earlier action: seems to know versus seems to have known.
• Voice convention: Both infinitives and gerunds have active and passive forms: to invite/to be invited and inviting/being invited.
• Complementation principle: The preceding noun, pronoun, verb, or adjective often determines whether an infinitive, a gerund, or either form is grammatical.

II. Phrasal Modals — Multi-word Expressions of Modality

Phrasal modals are multi-word expressions that convey meanings similar to central modal auxiliaries but behave partly like ordinary verb phrases.

A. Phrasal modals

Phrasal modals express obligation, probability, ability, intention, expectation, or necessity through combinations containing forms such as be, have, and used.

• Obligation and necessity: Have to, have got to, and need to indicate that circumstances or rules require an action.
  • Employees have to wear identification cards.
  • Unlike must, have to readily changes tense: had to leave, will have to leave.
• Expectation: Be supposed to identifies a duty, arrangement, or generally accepted expectation: The report is supposed to arrive today.
• Planned future: Be going to expresses an intention or a prediction based on present evidence: The clouds are dark; it is going to rain.
• Ability or opportunity: Be able to substitutes for can where a non-finite or perfect form is needed: She has been able to recover the data.
• Habit in the past: Used to describes a past state or repeated action that no longer holds: They used to communicate by fax.
• Immediate or scheduled action: Be about to indicates the very near future, while be to often signals an official plan:
  • The presentation is about to begin.
  • The delegates are to meet on Monday.
• Negative and interrogative forms: Most phrasal modals use do or inflect be/have: Do we have to wait?; She is not supposed to enter.
• Register distinction: Must can sound direct or speaker-imposed; have to often presents obligation as externally determined.

B. Functional limits and selection

Phrasal modals are not completely interchangeable with central modals because tense, register, and source of modality affect selection.

• Past necessity: Had to is normally used for an actual past requirement: We had to cancel the call.
• Absence of necessity: Do not have to means “it is unnecessary,” whereas must not means “it is prohibited.”
• Past habit limitation: Used to can describe states—used to know—but would normally describes repeated actions, not states.
• Contraction: Informal speech permits forms such as going to pronounced as “gonna,” but formal written communication retains the full form.

III. Complex Modals — Modality with Aspect and Voice

Complex modals combine a modal auxiliary with perfect, progressive, or passive auxiliaries to locate a judgment in time or alter its aspect and voice.

A. Complex modals

A complex modal follows an ordered auxiliary structure in which each auxiliary determines the form immediately after it.

modal + have + been + being + past participle

Here, modal expresses modality, have marks perfect aspect, been supports progressive or passive structure, being marks an ongoing passive process, and the past participle carries the lexical meaning.

• Modal perfect: modal + have + past participle refers to a completed or earlier situation.
  • She may have misunderstood the message expresses uncertain past possibility.
  • You should have replied expresses an unfulfilled past obligation or criticism.
• Modal progressive: modal + be + present participle presents an action as ongoing: They must be waiting outside.
• Modal passive: modal + be + past participle focuses on the receiver of an action: The complaint must be investigated.
• Perfect progressive: modal + have been + present participle describes an activity continuing over a period before the reference point: He may have been working overnight.
• Perfect passive: modal + have been + past participle places a passive event before the present judgment: The file could have been deleted accidentally.
• Order restriction: English auxiliaries occur in a fixed sequence—modal, perfect, progressive, passive, lexical verb. Forms such as have may left are therefore ungrammatical.
• Negative placement: Not follows the modal: might not have been received.
• Deduction scale: Must have signals strong positive inference, may/might/could have weaker possibility, and cannot have strong negative inference.

B. Interpretation and communication

Complex modals allow speakers to distinguish facts from judgments, but context determines their exact force.

• Counterfactual result: Could have succeeded often means success was possible but did not occur.
• Uncertain result: In The team could have arrived already, the arrival may actually have occurred.
• Professional caution: The figures may have been misreported appropriately limits certainty when evidence is incomplete.
• Structural economy: Extremely long combinations such as might have been being monitored are grammatical but stylistically heavy; clearer rephrasing is often preferable.

IV. Simple Infinitives and Gerunds — Basic Non-finite Complements

Simple infinitives and gerunds use the base forms to + verb and verb-ing without perfect marking.

A. Simple infinitives and gerunds

The simple infinitive typically views an action prospectively or abstractly, while the simple gerund treats an activity as a process, experience, or noun-like concept.

1. Simple infinitive

   • Form: to + base verb, as in to speak; after modals and certain verbs, the bare infinitive appears: can speak, let her speak.
   • Purpose: It answers “for what purpose?”: He called to confirm the appointment.
   • Subject complement: Her objective is to improve client relations.
   • Negation: Not precedes the infinitive: They decided not to disclose the password.

2. Simple gerund

   • Form: verb + -ing, as in speaking.
   • Subject function: Listening prevents misunderstanding.
   • Object function: She enjoys negotiating.
   • Prepositional complement: They succeeded by cooperating; after a preposition, a gerund is normally required.
   • Negation: Not precedes the gerund: Not responding may appear discourteous.

• Shared verb properties: Both forms can take objects and adverbials: to deliver the message clearly; delivering the message clearly.
• Number agreement: A gerund clause used as a subject is normally singular: Working long hours is exhausting.
• Possessive subject: Formal usage may mark the gerund’s subject possessively: We appreciated Rina’s helping us.

B. Meaning contrasts

Changing between an infinitive and a gerund can preserve meaning, slightly alter emphasis, or create a completely different interpretation.

• Small difference: Like reading emphasizes enjoyment; like to read before bed may emphasize habit or preference.
• Remember/forget: Remember doing recalls an earlier event; remember to do means not failing to perform a later duty.
• Stop: Stop talking means discontinue the activity; stop to talk means pause another activity for that purpose.
• Try: Try restarting the device proposes an experiment; try to restart it emphasizes effort.
• Regret: Regret saying it concerns a past action; regret to inform you introduces unwelcome present communication.

V. Complex Infinitives and Gerunds — Perfect, Progressive, and Passive Forms

Complex infinitives and gerunds express relationships of anterior time, duration, and voice more precisely than their simple forms.

A. Complex infinitives and gerunds

Complex non-finite constructions combine infinitive or gerund markers with perfect, progressive, or passive auxiliaries.

1. Complex infinitives

   • Perfect: to have + past participle marks earlier action: She appears to have completed the survey.
   • Progressive: to be + present participle marks ongoing action: He seems to be listening.
   • Passive: to be + past participle shifts focus to the receiver: The form needs to be signed.
   • Perfect passive: to have been + past participle: The email is believed to have been intercepted.

2. Complex gerunds

   • Perfect: having + past participle explicitly marks earlier action: He denied having copied the document.
   • Passive: being + past participle: She disliked being interrupted.
   • Perfect passive: having been + past participle: They resented having been excluded.
   • Perfect progressive: having been + present participle: He admitted having been working elsewhere.

• Time relationship: In She claims to have sent it, the sending precedes the claiming.
• Simple-form alternative: When sequence is already obvious, English often prefers the simpler gerund: He apologized for arriving late rather than for having arrived late.
• Logical subject: An object can identify the performer of an infinitive: We expected the courier to arrive.
• Stylistic control: Complex forms improve precision but become cumbersome when auxiliary chains add no necessary time or voice distinction.

VI. Complement Patterns — Selection after Other Word Classes

Infinitive and gerund complements are governed by established grammatical patterns associated with particular nouns, pronouns, verbs, and adjectives.

A. Nouns, pronouns, verbs and adjectives with infinitives and gerunds

The controlling word and intended meaning determine which non-finite form follows.

• Nouns with infinitives: Abstract nouns often take a to-infinitive that specifies their content or purpose: a decision to resign, an opportunity to speak, the ability to adapt.
• Nouns with gerunds: Nouns followed by a preposition take a gerund: a reason for leaving, difficulty in communicating, the advantage of planning.
• Pronouns with infinitives: Indefinite or interrogative pronouns may be modified by an infinitive: something to discuss, nobody to contact, what to say.
• Object pronouns before infinitives: Objective case identifies the infinitive’s logical subject: They asked him to wait, not he to wait.
• Possessives before gerunds: Formal constructions use possessive forms: We objected to their interrupting the meeting.
• Verbs taking infinitives: Agree, decide, hope, intend, manage, offer, plan, promise, and refuse commonly take to + verb: She promised to respond.
• Verbs taking gerunds: Admit, avoid, consider, deny, enjoy, finish, postpone, and suggest commonly take -ing: They postponed launching the service.
• Verb + object + infinitive: Advise, allow, ask, encourage, expect, persuade, and want can introduce an object: We encouraged them to participate.
• Adjectives with infinitives: Evaluative and emotional adjectives commonly take infinitives: ready to begin, pleased to help, difficult to explain.
• Adjectives with preposition + gerund: Fixed adjective-preposition combinations require gerunds: interested in learning, responsible for checking, afraid of failing.
• Preposition test: In look forward to meeting, to is a preposition, not an infinitive marker; therefore the gerund meeting is required.